Volcanoes Q&A
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Dec 6, 2023
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Volcanoes Q&A
1. What is the difference between magma and lava?
Magma is melted rock. Lava is when magma reaches the surface.
2. What is a silicate?
Silicate refers to the basic structure of most rocks and minerals: one silicone atom combined with four oxygen atoms.
3. How does the amount of silica affect how a lava flows?
The amount of silica affects the fluidity and speed of lava flows.
4. What does silica do in a lava to make it thicker?
Silicates polymerize (form chains) and thicken liquids.
5. What property did Kilaeua’s crater share up until 2018 with Ethiopia’s volcano Erte Ale?
An active lava lake.
6. Looking at the andesite rock in Slide #3, how did those large white crystals form?
When magma cools in the magma chamber, it precipitates mineral crystals.
7. How does the crystallization of magma differ from water?
Magma doesn’t solidify at one temperature; the mineral crystals form sequentially.
8. How does the top diagram in Slide #3 label the mixture of liquid magma and crystal solids? Crystal mush.
9. What are the two main gases in magma?
Water and carbon dioxide.
10. When gases are no longer dissolved in magma or soda, what do they form?
They form explosive bubbles.
11. What force keeps gases dissolved in a liquid?
Pressure.
12. In the left side photo in Slide #4, what substance is rapidly cooling the lava?
A sheet of ice.
13. Which lava in the table has the highest temperature and the lowest silica content?
Basalt.
14. Why does basalt form shield volcanoes?
Basalt forms shield volcanoes due to its low silica, high iron content, and higher temperatures, allowing lava to flow easily.
15. What allows andesite to form steep sided stratovolcanoes?
Andesite is a thicker lava that forms steep-sided stratovolcanoes due to its medium silica content and temperature.
16. What are three reasons that rhyolite is so explosive?
Rhyolite is the thickest lava type and has high silica content, dissolved gases, and low temperatures.
17. What is more viscous – a hot fluid or a cold fluid?
Hot fluid.
18. What are two properties of basalt that would help you identify the rock when walking along
Mt. Baldy Road?
Its color and texture.
19. What type of volcano is Amboy crater?
A cinder cone.
20. There are a lot of varieties of andesite in Mt. Baldy canyon. How would you describe andesite from looking at the photo in Slide #7?
Andesite looks like a grey rock with salt-and-pepper-colored minerals.
21. What causes stratovolcanoes to be so steeped sided?
Thicker andesite lava doesn’t flow far and builds up the steep slopes.
22. Strato in stratovolcano means layered. What are the two layers of this type of volcano?
Volcanic ash and lava flows.
23. Rhyolite is high in silica and low in iron. What color does that give andesite?
Rhyolite is light-colored (felsic). Andesite is intermediate.
24. Why is rhyolitic ash common but not rhyolite lava?
Super volcanoes mainly produce rhyolite ash.
25. What type of volcano is Yellowstone?
A supervolcano.
26. With a super volcano, you don’t have a mountain. So, what creates the huge depression after an eruption?
The explosive rhyolite magma.
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